An arrow nock forms the rearward end of an arrow and generally has a pair of wings that form a notch for receiving the bowstring. An arrow nock without a notch is disclosed in U.S. Pat. No. 1,785,589 to Mead. The arrow nock is often made as a separate component that is affixed to the rearward end of the arrow shaft.
Arrow nocks with a notch having parallel sides or sides that diverge rearwardly can slip off of the bowstring as the bow is drawn. Many known arrow nocks have notches with sides that converge rearwardly to retain the nock on the bowstring. However, the rearwardly converging sides create frictional drag on the arrow during release from the bowstring.
U.S. Pat. No. 1,542,762 to Cole discloses an arrow nock where one of the wings is spring biased and pivots to accommodate different bowstring diameters. U.S. Pat. No. 3,034,789 to Moore discloses an arrow nock with a leaf spring to retain the arrow on the bowstring. U.S. Pat. No. 3,214,174 to Saunders discloses an arrow nock with a cavity forward of the notch that allows the wings to flex outwardly more easily during engagement and release of the bowstring. None of these arrow nocks eliminates frictional drag during release.